1. Field of the Invention
The present invention relates to an ink-jet printing head applicable to an image-recording apparatus arranged to perform a recording operation on a recording medium, with an ink delivered from nozzles.
2. Discussion of Related Art
There is known an ink-jet printing head of a type including a cavity unit and a piezoelectric actuator formed on the cavity unit. The cavity unit has a common manifold chamber from which an ink supplied from an ink supply source is distributed to a plurality of pressure chambers through which the ink is delivered to respective nozzles. When the ink in the selected pressure chambers is pressurized by the piezoelectric actuator, the pressurized ink in each selected pressure chamber is fed to the corresponding nozzle, and is ejected from this nozzle.
In the ink-jet printing head constructed as described above, each pressure chamber is in communication with both of the corresponding nozzle and the common manifold chamber, so that a pressure wave of the ink generated upon pressurization of the ink in the pressure chamber by the piezoelectric actuator has not only a forward component propagating toward the nozzle, but also a rearward component propagating toward the common manifold chamber. The rearward component of the pressure wave generates a so-called “cross talk” in which the rearward component propagates to the other nozzles through the common manifold chamber. This cross talk causes degradation of printing quality of the ink-jet printing head. To prevent the cross talk, it is known to provide the common manifold chamber with a damper which absorbs the rearward component of the pressure wave.
For example, JP-2003-11356 A (FIGS. 2-5) and US 2004001124 A1 (FIGS. 2 and 3) corresponding to JP-2004-25636 A disclose a cavity unit consisting of a plurality of plates laminated o each other, which include a nozzle plate having nozzles, a damper plate having a damper chamber, and a manifold plate having a common manifold chamber. The manifold plate and the damper plate are laminated on each other such that the common manifold chamber and the damper chamber are located adjacent to each other in the direction of lamination of those plates. In this arrangement, the cavity unit has a smaller surface area in cross section taken in a plane perpendicular to the direction of lamination, than in an arrangement in which the common manifold chamber and the damper chamber are formed in a single plate such that these two chambers are located adjacent to each other in the direction perpendicular to the direction of lamination of the cavity unit. Accordingly, the ink-jet printing head has a reduced overall size.
Described in greater detail, the cavity unit disclosed in JP-2003-11356 A uses the manifold plate formed of a metallic material such that the common manifold chamber takes the form of a recess which is formed in the manifold plate and which is partly defined by a thin bottom wall. The manifold plate is laminated on the damper plate such that the thin bottom wall of the recess serves as a top wall of the damper chamber. On the other hand, the cavity unit disclosed in US 2004001124 A1 uses the damper plate formed of a metallic material such that the damper chamber takes the form of a recess which is formed in the damper plate and which is partly defined by a thin top wall. The manifold plate is laminated on the damper plate such that the thin top wall of the damper chamber serves as a bottom wall of the common manifold chamber. In both of these cavity units, one of the opposite surfaces of the above-described thin wall partly defines the common manifold chamber while the other surface of the thin wall is exposed to an air space. In this arrangement, the rearward component of the pressure wave propagating from the pressure chamber to the common manifold chamber through a communication hole is absorbed by oscillation of the above-described thin wall of the metallic material.
In the cavity units disclosed in the above-identified two publications wherein the pressure wave propagating to the common manifold chamber is absorbed by the metallic thin wall, it is necessary to form the thin wall with a minimum thickness and/or a relatively large surface area, for effectively absorbing the pressure wave by a sufficiently large magnitude of oscillation of the thin wall.
However, there is a limitation in the reduction of the thickness of the thin wall with high accuracy by increasing the thickness of the above-described recess formed in the metallic manifold plate or damper plate. Further, an increase of the surface area of the thin wall gives rise to a problem of an increased size of the ink-jet printing head.